fdk128 is better than ffa128, fdk96k, ffa96k, fdk64k, ffa64kffa128 is better than ffa96k, fdk64k, ffa64kfdk96k is better than ffa96k, fdk64k, ffa64kffa96k is better than ffa64kfdk64k is better than ffa64k

I also read some people suggesting that the ffmpeg implementation sounds as good or better than fdk ... which is clearly nonsense.

They are probably just repeating the wild claim that was made in the announcement in FFmpeg's front page:

Quote

The encoder is transparent at 128kbps for most samples tested with artifacts only appearing in extreme cases. Subjective quality tests put the encoder to be of equal or greater quality than most of the other encoders available to the public.